Answer
$$HC_2H_3O_2(aq) + NaHSO_3(aq) \longrightarrow SO_2(g) + H_2O(l) + NaC_2H_3O_2$$
Work Step by Step
1. This reaction has a sulfite and an acid as its reactants. Thus, it will produce $SO_2(g)$, $H_2O(l)$ and a salt made of the other ions:
$$HC_2H_3O_2(aq) + NaHSO_3(aq) \longrightarrow SO_2(g) + H_2O(l) + Salt$$
The remaining ions are: $Na^{+}$ and $C_2H_3{O_2}^-$, therefore, the salt is $NaC_2H_3O_2$:
$$HC_2H_3O_2(aq) + NaHSO_3(aq) \longrightarrow SO_2(g) + H_2O(l) + NaC_2H_3O_2$$
2. Now, balance the equation.
The equation is already balanced.
